When a specially-designed current probe is clamped to a conductive structure, such as a ship's mast, the combination of the current probe and mast can function as an antenna (hereinafter referred to as a mast clamp current probe (MCCP) antenna). Current probes used in MCCP antenna applications must be specifically designed for the platform on which the current probe will be used. In order to properly match the current probe to the structure, the current probe designer needs to know the characteristic impedance of the structure. The “characteristic impedance” is the impedance of the structure that the probe will see. Previously the characteristic impedance of the structure was determined by feeding a brass, scale model of the structure as if it were an antenna.